The big selling point here is the water repellency of the Nanoflex. Castelli use their Thermoflex (a brush-backed Roubaix) fabric with the addition of "tiny silicone nanofilaments on the surface". This results in water beading up and rolling off.

Castelli don't claim that Nanoflex is completely waterproof. It'll keep road spray and showers out but harder rain does work through, especially through the bit at the front of your knee that you stretch repeatedly as you pedal. But the point is, these feel like any other leg warmers in terms of feel and breathability – like most, they're made from nylon and Lycra – so there's no down side to that extra water repellency.

How long does the Nanoflex keep doing its job? Well, I did a little test and found that the knee warmers I have from a couple of years ago that have been through the washing machine a zillion times weren't doing much in the way of keeping water out any more. Arm warmers from about a year ago that have been through the wash a couple of dozen times were still doing well.

I contacted Castelli's UK distributor, Saddleback, to find out if that was to be expected and they said: "Light ironing over the surface will rejuvenate the protection."

That's what I did and – hey presto! – it worked. I wouldn't say that the performance is right back to original levels, but it's not far off.

Nanoflex aside, these are good leg warmers in their own right, coming with just one flatlock stitched seam up the back, which I haven't found at all irritating. The elasticated gripper has silicone on the inside to hold it against your leg, and on the outside to keep it in place against your shorts. I've never had any trouble there. A YKK zip at the back makes getting them on and off easy, even over your shoes.

Castelli give a temperature range for every item of their clothing and we usually agree with them. In this case, they say 8-16°C. You could wear these when it's a little colder than that, but chances are that if it's that nippy there's no chance you'll want to remove your leg warmers mid-ride, so you might as well go for tights.

Verdict

Warm, comfortable leg warmers with the added bonus of being water repellent.

road.cc test report

Make and model: Castelli Nanoflex Leg Warmer

Size tested: Large, Black, 2 sent

Tell us what the product is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Castelli say, "We always strive for total performance and total innovation, but sometimes we surprise ourselves. This NanoFlex fabric behaves just like our Thermoflex fabric in dry conditions, but then provides unbelievable water repellency when it starts raining. We don't claim that it's fully waterproof, but it's the most effective thing we've ever made for keeping you comfortable in all conditions. It's just barely short of a miracle."

Rate the product for quality of construction:

8/10

Rate the product for performance:

8/10

Rate the product for durability:

7/10

The logos started to crack quite soon, but that doesn't affect performance.

Rate the product for comfort, if applicable:

8/10

Rate the product for value:

6/10

Did you enjoy using the product? Yes.

Would you consider buying the product? Yes.

Would you recommend the product to a friend? Yes.

Overall rating: 8/10

About the tester

Age: 43 Height: 190cm Weight: 75kg

I usually ride:My best bike is:

I've been riding for: Over 20 years I ride: Most days I would class myself as: Expert

I regularly do the following types of riding: commuting, club rides, sportives, general fitness riding,

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Mat has worked for loads of bike magazines over 20+ years, and been editor of 220 Triathlon and Cycling Plus. He's been road.cc technical editor for eight years, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a past winner of the Cycling Media Award for Specialist Online Writer.

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